This invention relates to protective coatings and, more particularly, to gas turbine engine components having a protective coating on selected portions thereof.
Components that are exposed to high temperatures, such as a turbine of a gas turbine engine, typically include a coating to protect the component from oxidation and corrosion. For example, turbine blades and vanes may include a protective coating on the blade airfoil portion that resists corrosion from hot gases flowing over the airfoil.
Although effective, such protective coatings may debit mechanical properties of the component. For example, protective coatings are often more brittle than superalloy materials typically used to make the component, and some coatings may interdiffuse with the superalloy to form localized brittle regions. Under fatigue conditions in a gas turbine engine, the coating and/or the localized brittle regions may cause fatigue cracking and thereby limit the useful life of the component. Additionally, the coating adds weight to the component without adding structural strength, which may require stronger or heavier components in order to achieve a desired durability.
Accordingly, there is a need for a protective coating that is disposed only on certain areas of a component to protect those areas from corrosion while maintaining mechanical properties of other uncoated areas. This invention addresses those needs while avoiding the shortcomings and drawbacks of the prior art.